diff --git a/lib/csslib.php b/lib/csslib.php
index 27e24c7013e..6ab108a478c 100644
--- a/lib/csslib.php
+++ b/lib/csslib.php
@@ -566,14 +566,17 @@ class css_optimiser {
                                     $currentprocess = self::PROCESSING_SELECTORS;
                                 }
                             }
-                            $buffer = '';
-                            $currentatrule = false;
+                            if ($currentatrule !== 'media') {
+                                $buffer = '';
+                                $currentatrule = false;
+                            }
                             // continue 1: The switch processing chars
                             // continue 2: The switch processing the state
                             // continue 3: The for loop
                             continue 3;
                         case '{':
-                            if ($currentatrule == 'media' && preg_match('#\s*@media\s*([a-zA-Z0-9]+(\s*,\s*[a-zA-Z0-9]+)*)#', $buffer, $matches)) {
+                            if ($currentatrule == 'media' && preg_match('#\s*@media\s*([a-zA-Z0-9]+(\s*,\s*[a-zA-Z0-9]+)*)\s*{#', $buffer, $matches)) {
+                                // Basic media declaration
                                 $mediatypes = str_replace(' ', '', $matches[1]);
                                 if (!array_key_exists($mediatypes, $medias)) {
                                     $medias[$mediatypes] = new css_media($mediatypes);
@@ -581,6 +584,14 @@ class css_optimiser {
                                 $currentmedia = $medias[$mediatypes];
                                 $currentprocess = self::PROCESSING_SELECTORS;
                                 $buffer = '';
+                            } else if ($currentatrule == 'media' && preg_match('#\s*@media\s*([^{]+)#', $buffer, $matches)) {
+                                // Advanced media query declaration http://www.w3.org/TR/css3-mediaqueries/
+                                $mediatypes = $matches[1];
+                                $hash = md5($mediatypes);
+                                $medias[$hash] = new css_media($mediatypes);
+                                $currentmedia = $medias[$hash];
+                                $currentprocess = self::PROCESSING_SELECTORS;
+                                $buffer = '';
                             } else if ($currentatrule == 'keyframes' && preg_match('#@((\-moz\-|\-webkit\-)?keyframes)\s*([^\s]+)#', $buffer, $matches)) {
                                 $keyframefor = $matches[1];
                                 $keyframename = $matches[3];
diff --git a/lib/tests/cssslib_test.php b/lib/tests/cssslib_test.php
index 278d2866d50..f73ba258012 100644
--- a/lib/tests/cssslib_test.php
+++ b/lib/tests/cssslib_test.php
@@ -72,6 +72,7 @@ class css_optimiser_testcase extends advanced_testcase {
         $this->try_invalid_css_handling($optimiser);
         $this->try_bulk_processing($optimiser);
         $this->try_break_things($optimiser);
+        $this->try_media_rules($optimiser);
         $this->try_keyframe_css_animation($optimiser);
     }
 
@@ -994,6 +995,39 @@ CSS;
 @-webkit-keyframes mymove {0%{top:10px;}12%{top:40px;}30%{top:20px;}65%{top:35px;}100%{top:9px;}}
 CSS;
         $this->assertEquals($cssout, $optimiser->process($cssin));
+    }
 
+    public function try_media_rules(css_optimiser $optimiser) {
+        $cssin = "@media print {\n  .test{background-color:#333;}\n}";
+        $cssout = "@media print {\n  .test{background-color:#333;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
+
+        $cssin = "@media screen and (min-width:30px) {\n  #region-main-box{left: 30px;float: left;}\n}";
+        $cssout = "@media screen and (min-width:30px) {\n  #region-main-box{left:30px;float:left;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
+
+        $cssin = "@media all and (min-width:500px) {\n  #region-main-box{left:30px;float:left;}\n}";
+        $cssout = "@media all and (min-width:500px) {\n  #region-main-box{left:30px;float:left;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
+
+        $cssin = "@media (min-width:500px) {\n  #region-main-box{left:30px;float:left;}\n}";
+        $cssout = "@media (min-width:500px) {\n  #region-main-box{left:30px;float:left;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
+
+        $cssin = "@media screen and (color), projection and (color) {\n  #region-main-box{left:30px;float:left;}\n}";
+        $cssout = "@media screen and (color),projection and (color) {\n  #region-main-box{left:30px;float:left;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
+
+        $cssin = "@media print {\n  .test{background-color:#000;}\n}@media print {\n  .test{background-color:#FFF;}\n}";
+        $cssout = "@media print {\n  .test{background-color:#FFF;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
+
+        $cssin = "@media screen and (min-width:30px) {\n  #region-main-box{background-color:#000;}\n}\n@media screen and (min-width:30px) {\n  #region-main-box{background-color:#FFF;}\n}";
+        $cssout = "@media screen and (min-width:30px) {\n  #region-main-box{background-color:#FFF;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
+
+        $cssin = "@media screen and (min-width:30px) {\n  #region-main-box{background-color:#000;}\n}\n@media screen and (min-width:31px) {\n  #region-main-box{background-color:#FFF;}\n}";
+        $cssout = "@media screen and (min-width:30px) {\n  #region-main-box{background-color:#000;}\n}\n\n@media screen and (min-width:31px) {\n  #region-main-box{background-color:#FFF;}\n}";
+        $this->assertEquals($cssout, $optimiser->process($cssin));
     }
 }
\ No newline at end of file